The field of the disclosure relates generally to engine nacelles, and, more particularly, to a lipskin assembly for an engine nacelle.
At least some known engines, such as some known jet engines and turbofan jet engines, are surrounded by a generally barrel-shaped nacelle. At least some known nacelles include a lipskin that extends in an upstream direction from a first edge to a hilite, that is, a locus of forwardmost points on the lipskin, to define a generally diffuser-shaped inlet of the nacelle. Such known lipskins also extend radially outward and back from the hilite in a downstream direction to a second edge to form at least a portion of a generally aerodynamic radially outer barrel of the nacelle.
At least some known lipskins include at least a portion that is unitarily formed from the first edge, through the hilite, to the second edge. Such unitary forming is customarily used to reduce a need for transverse weld lines or other couplings that may result in a premature transition from natural laminar air flow to turbulent air flow over the outer barrel portion of the lipskin. For example, at least some known lipskins are formed by spin-forming a unitary blank of titanium or 2219 aluminum into an approximate shape of the lipskin, and then performing a series of machining and/or stretch-forming operations on the unitary lipskin until it meets tolerance and surface finish requirements. However, such multi-stage forming is costly and time-consuming. Moreover, stretch-forming of such known unitary lipskins is relatively difficult due to a curvature around the hilite of the lipskin, which may require, for example, a “bull nose” fixture and jaws to perform stretch-forming.
In addition, even after multi-stage forming, such known unitary lipskins may exhibit ripples or waves on the outer barrel portion. Furthermore, for at least some known nacelles, a limit on a size of unitary lipskin assemblies that may be formed from spin-forming results in a need for close-out panels on the outer barrel downstream of the second edge of the lipskin, for example, between the second edge and a fan cowl. Such ripples, waves, and/or close-out panels on the outer barrel tend to cause a premature transition to turbulent air flow over the nacelle, which increases a specific fuel consumption of the engine.